Shielded luminaire

ABSTRACT

An improved radiation shielded luminaire utilizing gas discharge lamps. Shielding of radio frequency radiation is provided by a grounded superimposed screen and louver assembly. Additional shielding around the cathode area of the lamp shields radiation in the frequency ranges of x-ray and infrared radiation.

United States Patent 1191 Oil 1 SHIELDED LUMINAIRE [75] Inventor: JohnNash Ott, Sarasota, Fla.

[73] Assignee: John Ott Laboratories, Sarasota,

Fla,

[22] Filed: Dec. 3, 1973 [21] Appl. No.: 421,253

11] 3,885,150 1451 May 20, 1975 OTHER PUBLICATIONS Ficchi, R. F.,Electrical Interference," Hayden Book Co.1nc., N.Y., 1964, pp. 106-107.

[52] US. Cl 240/4639; 174/35 MS; 313/324 51 1111. CL. F2lv 11/06 PrimaryExaminer-Alfred Smith [58] Field of Search 313/112, 324, 313; AssistantExaminer-Wm Punter 249 4 39 4 51 5111 74 35 MS Atmrney, Agent, orFirm-Richard E. Hosley [56] References Cited [57] ABSTRACT UNITED STATESPATENTS An improved radiation shielded luminaire utilizing gas 2,272,2742/1942 Pieper ..240/51.11 R discharge p Shielding Of radio frequencyradia- 2,368,376 l/1945 Peters et a1 123/148 P tiOn is provided by agrounded superimposed screen 2,509,979 5/1950 Marti 174/35 MS and louverassembly. Additional shielding around the 3,231,663 1/1966 Schwartz...240/463 cathode area of the lamp shields radiation in the fre- 3,253,0825/1966 Buset 174/35 quency ranges f Hay and i f d radiation. 3,265,8048/1966 Berger et al..... 174/35 MS 0 I 3,305,623 l/1967 Bakker et a1 17435 MS 5 Clalms, 4 Drawing g s '5 JIIII/IIIIIIIIIIIIIIIQPIIIIIIIIIIIIIIIIIIIIIIIJ ,ggmggxammsm 3885150I/I/II/III/[IIIII/II/I/IIIIIIII/IIIIIIIIII/III FIG. 4

SHIELDED LUMINAIRE BACKGROUND OF THE INVENTION The present inventionrelates to luminaires having gas discharge type light sources and. moreparticularly, to an improved shielding arrangement which will suppressundesirable electromagnetic radiation while transmitting light in thefrequency range of natural daylight.

It has been known for some time that gas discharge lamps such asfluorescent, mercury and sodium vapor and other similar lamps produceand emit electromag netic radiation in the radio frequency (RF) spectrumand that such radiation causes interference with radio and otherelectronic measuring, testing and communicating equipment. Morerecently, it has become known that such radiation produces biologicalresponses in plants. It is also believed to have an effect on animalsand human beings by affecting the endocrine and central nervous systems.These biological effects are exceedingly complex and appear to involvean interplay of radiation in a number of different frequency ranges. Oneconclusion now evident is that natural light is a very important factoraffecting life on earth and that artificial light sources shouldapproach natural daylight in spectral distribution and intensity asclosely as possi ble. This means that other kinds of radiation presentin artificial light sources such as gas discharge lamps should beshielded since it may have an adverse effect on life as a form ofradiation pollution. Radiation shielding heretofore used in gasdischarge lamps and luminaires to prevent interference with electronicequipment is not completely adequate to prevent unwanted biologicalresponses because of the wider frequency range of the radiation involvedwhich requires shielding. Also, the shielding should not prevent thetransmission from the luminaire of beneficial radiation found in naturaldaylight such as ultraviolet when the full-spectrum lamps, nowcommercially available, are used for illumination.

Accordingly, it is an object of this invention to provide an improvedluminaire radiation shielding arrangement that will suppress unwantedradiation in a wide frequency range but not attenuate radiation in thefrequency range of natural daylight.

Another object of the invention is to provide a shielded luminaireconstruction that is relatively sirn' ple, inexpensive to manufactureand which can be easily applied to luminaires of conventionalconstruction.

Further objects and advantages of the invention will become apparent asthe following description proceeds.

SUMMARY Briefly, in accordance with the invention a luminaire isprovided with a housing having an opening through which light from thelamps passes. The opening is covered by a louver assembly comprisingcrossed fins forming a plurality of open cells through which lightpassesv Supported on the louver assembly on the lamp side is aconductive screen having mesh openings large enough to pass asubstantial amount oflight but smaller than the louver cells. Thehousing, louver assembly and screen are grounded to provide RF shieldingof the enclosed lamps over an extended frequency range. Visible andultraviolet light passing directly to the illuminated area through theopenings in the screen and louver are not attenuated. The louver alsoprovides glare shielding of visible light in the usual way. Shielding ofunwanted radiation in the infrared and x-ray frequency ranges isprovided by additional shields encircling the cathodes of the lamps.

For a better understanding of the invention, reference should be made tothe following detailed description taken in connection with theaccompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a luminaire embodying theshielding construction of the present invention.

FIG. 2 is a partial sectional side view of the luminaire of FIG. 1.

FIG. 3 is a perspective view illustrating constructional details of thelouver assembly.

FIG. 4 shows the screen used in the shielding construction.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring to FIG. 1, there isshown by way of an example a fluorescent lamp luminaire of the recessedtype adapted for a flush mounting on a ceiling. The luminaire comprisesa housing 10 formed of a suitable electrically conducting material suchas aluminum. Illumination is provided by one or more tubular fluorescentlamps, one of which is shown and designated by the number 11. Mountingsockets 12 carried on the housing sides 13 receive the lamp pins 14which are energized from a power source 15 through the usual ballast andstarting equipment (not shown). In order to provide illumination havingin the visible light range a spectral composition similar to daylight afull-spectrum fluorescent lamp is preferably used. Such lamps are nowcommercially available and the construction of such a lamp is shown, forexample, in US. Pat. No. 3,670,l93, issued June 13, 1972. Such lampsemit, in addition to visible light, middle and rear ultraviolet (UV) inabout the same ratio as found in natural daylight and the emission ofsuch UV is believed to be im portant from a health standpoint where thelamps are used for general illumination.

The housing 10 has a bottom opening 16 through which light from lamp 11passes into the illuminated area. The opening is covered by a louverassembly 17 of the so-called egg crate type, the construction of whichis shown in FIG. 3. As shown the louver assembly comprises a pluralityof perpendicular crossed fins 18 and 19 secured together in any suitablemanner to form a rigid construction. Light from lamp 11 passes throughcells 20 formed by the crossed fins l8 and 19. The fins control thelight distribution from the lamp in the usual way by cutting off directlight from the lamp 11 at socalled glare angles exceeding apredetermined angle with respect to the vertical. This is illustrated inFIGv 2 where a light ray A from lamp ll passes through a cell 20 to theillumined area below. On the other hand, a light ray B leaving the lampin the glare angle range is intercepted by fin 19.

For convenience in servicing the luminaire, the louver assembly 17 issuspended on pivots 21 so that it can be swung down on one side to giveaccess to the interior of the luminaire.

As pointed out above, gas discharge lamps are known to generate and emitelectromagnetic radiation in the range of the Hertzian or radio wavesand for the reasons stated, it is desirable to prevent such radiation bysuitable shielding. According to the invention, shielding is providedthat is effective over an extended fre quency range. A part of suchshielding is provided by the louver assembly. To this end, the fins 18and 19 are formed of an electrically conductive material such asaluminum and the assembly is electrically connected to ground potentialin any suitable manner as by a con nection designated by lead 22.

The attentuation of radio waves in a given frequency range passingthrough a grounded grid such as that provided by the crossed fins l8 and19 is a function of the grid size. The control of visible lightdistribution from the lamp is predetermined glare angle range asexplained above is also a function of grid size. Thus, if the grid sizeis fixed by light distribution considerations, the louver assembly willnot adequately attenuate radio waves in the higher frequency rangeswhere proper shielding is also considered important. Therefore, to givemore adequate radio wave shielding in a higher frequency rangeadditional shielding is provided as will now be described,

Supported on the top of the louver assembly so as to cover completelythe housing opening 16 is a wire mesh screen 23. The screen is formed bycrossed strands 24 and 25 of electrically conductive material. Theconstruction may, as shown, in FIGS. 1 and 4 be a Woven aluminum wiresimilar in construction to ordinary win dow screen. The screen iselectrically connected to ground potential in any suitable manner, theconnec tion being designated by the lead 26. Also grounded is theluminaire housing 10, this connection being designated by lead 27.

The mesh openings 28 of screen 23 are of sufficient size to permitpassage of light therethrough from the lamp 11 to the illuminated areawith reasonable efficiency. They are, however, as shown, considerablysmaller than the size of cells 20 in the louver assembly 17. For thatreason, the screen 23 attenuates radio waves in a higher frequency rangethan the louver assembly 17. Acting together, the louver assembly andscreen provide effective shielding of radio waves over an extendedfrequency range. This permits optimum design of the louver assembly withrespect to its light shielding function without sacrificing efficiencyof the radio wave shield. By way of an example, good results have beenobtained applying the invention to a luminaire having four 40 wattfluorescent lamps and having an opening 16 of 8 square feet. The size ofcells 20 was 1.75 X 1.75 inches square and the cell depth was 1 inch.The screen 23 used was woven aluminum screen having approximately 64mesh openings per square inch.

Because the screen 23 is made of a highly reflective material itreflects the ultraviolet as well as the visible light from thefluorescent lamp with good efficiency and without spectral distortion aswould be the case if a dark colored material such as copper were used.

Mounting the screen 23 above rather than below the louver assembly hasseverai advantages. First, the conductive screen is held by gravity infirm contact with the conductive fin members 18 and 19 maintaining goodelectrical contact for uniform ground potential distribution. Secondly,mounted in this position, any glare caused by reflection of light fromthe lamp by the 4 screen, as indicated, for example, by ray C in FIG, 2,will be shielded by the louver assembly.

In addition to radiation in the radio wave frequency range emanatingfrom the lamp, there is additional radiation from the electrode area ofthe lamp which should be shielded. For this purpose, there are providedcathode shields 29 and 30 which are mounted on the envelope of thefluorescent tube adjacent the ends so as to encircle the cathode area.These shields may be made by wrapping lead foil around the outside ofthe tube envelope, the foil being held in position by an adhesivecoating thereon. Cathode shields formed in this and other suitable waysare disclosed in US. Pat. No. 3,767,957, issued Oct. 23, 1973 andassigned to the same assignec as the present invention. By making thecathode shield of a high atomic number material such as lead they wiilabsorb electrode radiation in the fre' quency range of xrays as well asradiation on the infrared range both of which should be excluded fromthe luminaire light output to avoid radiation pollution.

In view of the foregoing, it will be apparent that there has beenprovided a luminaire that is relatively free of radiation pollutionwhile emitting the desired radiation of the natural daylight type,including the ultraviolet which is produced by full-spectrum lamps. Theu1travi olet component of such iight is preserved by the use of a highlyreflective radio wave screen. It is noted here that the use of a lightcontrol element utilizing a solid light transmission material such asglass absorbs the ultravioiet and is undesirable for that reason whenused with full'spectrurn lamps. It will also be apparent that thecombined screen and shield construction is simpie, inexpensive, and canbe easily applied to luminaires of the conventional type.

While there has been shown what is considered to be a preferredembodiment of the invention as applied to a luminaire utilizingfluorescent type gas discharge lamps, it will be apparent to thoseskilled in the art that various changes and modifications may be madewithout departing from the spirit and scope of the inven- KlOIl,

What is claimed new and desired to be secured by Letters Patent of theUnited States is:

l. A shielded luminaire comprising:

a housing formed of conductive material having a light-emitting openingtherein,

a gas discharge type lamp mounted within said housing so as to projectlight through said opening,

a light shielding louver assembly extending over said opening, saidassembly comprising a plurality of crossed tins formed of conductivematerial which form cells through which light from said lamp passes,

a mesh screen formed of crossed conductive strands extending across saidopening between said lamp and said louver assembly, and

connecting means electrically connecting to ground potential saidhousing, iouver assembly and screen,

the area of the screen mesh being sufficient to permit passage of lighttherethrough but smaller than the cell area of the louver assemblywhereby RF radia tion from said lamp is attenuated over an extendedfrequency range by action of the grounded screen and louver assemblywhile permitting passage of light from said lamp through the screen meshand louver ceils into the area illuminated by said lamp.

6 2. The shielded luminaire of claim 1 wherein the flective materialwhich will reflect light from the lamp screen is supported by the louverassembly. wilhou spectra] distortion h Shielded l'flmmalre of Claim 1mcludmg radm' 5. The shielded luminaire of claim 4 wherein the con tronshields extending around the cathode areas of the lamp 5 ductive strandsof the screen are formed of :1 material 4. The shielded luminaire ofclaim 1 wherein the conccmprislng aluminumductive strands of the screenare formed of a highly re-

1. A shielded luminaire comprising: a housing formed of conductivematerial having a light-emitting opening therein, a gas discharge typelamp mounted within said housing so as to project light through saidopening, a light shielding louver assembly extending over said opening,said assembly comprising a plurality of crossed fins formed ofconductive material which form cells through which light from said lamppasses, a mesh screen formed of crossed conductive strands extendingacross said opening between said lamp and said louver assembly, andconnecting means electrically connecting to ground potential saidhousing, louver assembly and screen, the area of the screen mesh beingsufficient to permit passage of light therethrough but smaller than thecell area of the louver assembly whereby RF radiation from said lamp isattenuated over an extended frequency range by action of the groundedscreen and louver assembly while permitting passage of light from saidlamp through the screen mesh and louver cells into the area illuminatedby said lamp.
 2. The shielded luminaire of claim 1 wherein the screen issupported by the louver assembly.
 3. The shielded luminaire of claim 1including radiation shields extending around the cathode areas of thelamp.
 4. The shielded luminaire of claim 1 wherein the conductivestrands of the screen are formed of a highly reflective material whichwill reflect light from the lamp without spectral distortion.
 5. Theshielded luminaire of claim 4 wherein the conductive strands of thescreen are formed of a material comprising aluminum.